So you want to drop your car off, get a service loaner, and then use that to go on vacation? I don't see why not, but be prepared to pay for the mileage... also, read the contract, it may specifically say you are not allowed to leave the state, exceed a certain distance, etc.

You need to get prior permission for over mileage and leaving the state

I remember a few years ago, our Merc was stuck in service for a couple weeks... we were pissed...
we had a vacation planned out of state and didn't want to lose it. We canned Merc NA and they authorized our dealer to give us permission to drive out out of state+not charge us for over mileage